| Message ID | 20240328135509.3755090-2-arnd@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 066afafc10c9476ee36c47c9062527a17e763901 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | wifi: ath: false-positive fortified-memset warnings | expand |
On Thu, Mar 28, 2024 at 02:55:04PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > The carl9170_tx_release() function sometimes triggers a fortified-memset > warning in my randconfig builds: > > In file included from include/linux/string.h:254, > from drivers/net/wireless/ath/carl9170/tx.c:40: > In function 'fortify_memset_chk', > inlined from 'carl9170_tx_release' at drivers/net/wireless/ath/carl9170/tx.c:283:2, > inlined from 'kref_put' at include/linux/kref.h:65:3, > inlined from 'carl9170_tx_put_skb' at drivers/net/wireless/ath/carl9170/tx.c:342:9: > include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > 493 | __write_overflow_field(p_size_field, size); > > Kees previously tried to avoid this by using memset_after(), but it seems > this does not fully address the problem. I noticed that the memset_after() > here is done on a different part of the union (status) than the original > cast was from (rate_driver_data), which may confuse the compiler. > > Unfortunately, the memset_after() trick does not work on driver_rates[] > because that is part of an anonymous struct, and I could not get > struct_group() to do this either. Using two separate memset() calls > on the two members does address the warning though. > > Fixes: fb5f6a0e8063b ("mac80211: Use memset_after() to clear tx status") > Link: https://lore.kernel.org/lkml/20230623152443.2296825-1-arnd@kernel.org/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Kees Cook <keescook@chromium.org>
On 3/28/24 2:55 PM, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > The carl9170_tx_release() function sometimes triggers a fortified-memset > warning in my randconfig builds: > > In file included from include/linux/string.h:254, > from drivers/net/wireless/ath/carl9170/tx.c:40: > In function 'fortify_memset_chk', > inlined from 'carl9170_tx_release' at drivers/net/wireless/ath/carl9170/tx.c:283:2, > inlined from 'kref_put' at include/linux/kref.h:65:3, > inlined from 'carl9170_tx_put_skb' at drivers/net/wireless/ath/carl9170/tx.c:342:9: > include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > 493 | __write_overflow_field(p_size_field, size); > > Kees previously tried to avoid this by using memset_after(), but it seems > this does not fully address the problem. I noticed that the memset_after() > here is done on a different part of the union (status) than the original > cast was from (rate_driver_data), which may confuse the compiler. > > Unfortunately, the memset_after() trick does not work on driver_rates[] > because that is part of an anonymous struct, and I could not get > struct_group() to do this either. Using two separate memset() calls > on the two members does address the warning though. > > Fixes: fb5f6a0e8063b ("mac80211: Use memset_after() to clear tx status") > Link: https://lore.kernel.org/lkml/20230623152443.2296825-1-arnd@kernel.org/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Sure... though I think AI-supported compilers will in the future nag about this again. Oh well! Acked-by: Christian Lamparter <chunkeey@gmail.com> > --- > I found this while testing randconfig builds, a .config that shows this > for me is at https://pastebin.com/yWFKvZYu > > Sorry I failed to follow up to Kees' request for a reproducer when > I posted this last year. > --- > drivers/net/wireless/ath/carl9170/tx.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c > index e902ca80eba7..0226c31a6cae 100644 > --- a/drivers/net/wireless/ath/carl9170/tx.c > +++ b/drivers/net/wireless/ath/carl9170/tx.c > @@ -280,7 +280,8 @@ static void carl9170_tx_release(struct kref *ref) > * carl9170_tx_fill_rateinfo() has filled the rate information > * before we get to this point. > */ > - memset_after(&txinfo->status, 0, rates); > + memset(&txinfo->pad, 0, sizeof(txinfo->pad)); > + memset(&txinfo->rate_driver_data, 0, sizeof(txinfo->rate_driver_data));
Arnd Bergmann <arnd@kernel.org> wrote: > The carl9170_tx_release() function sometimes triggers a fortified-memset > warning in my randconfig builds: > > In file included from include/linux/string.h:254, > from drivers/net/wireless/ath/carl9170/tx.c:40: > In function 'fortify_memset_chk', > inlined from 'carl9170_tx_release' at drivers/net/wireless/ath/carl9170/tx.c:283:2, > inlined from 'kref_put' at include/linux/kref.h:65:3, > inlined from 'carl9170_tx_put_skb' at drivers/net/wireless/ath/carl9170/tx.c:342:9: > include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > 493 | __write_overflow_field(p_size_field, size); > > Kees previously tried to avoid this by using memset_after(), but it seems > this does not fully address the problem. I noticed that the memset_after() > here is done on a different part of the union (status) than the original > cast was from (rate_driver_data), which may confuse the compiler. > > Unfortunately, the memset_after() trick does not work on driver_rates[] > because that is part of an anonymous struct, and I could not get > struct_group() to do this either. Using two separate memset() calls > on the two members does address the warning though. > > Fixes: fb5f6a0e8063b ("mac80211: Use memset_after() to clear tx status") > Link: https://lore.kernel.org/lkml/20230623152443.2296825-1-arnd@kernel.org/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Reviewed-by: Kees Cook <keescook@chromium.org> > Acked-by: Christian Lamparter <chunkeey@gmail.com> > Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com> 2 patches applied to ath-next branch of ath.git, thanks. 066afafc10c9 wifi: carl9170: re-fix fortified-memset warning 61752ac69b69 wifi: ath9k: work around memset overflow warning
diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c index e902ca80eba7..0226c31a6cae 100644 --- a/drivers/net/wireless/ath/carl9170/tx.c +++ b/drivers/net/wireless/ath/carl9170/tx.c @@ -280,7 +280,8 @@ static void carl9170_tx_release(struct kref *ref) * carl9170_tx_fill_rateinfo() has filled the rate information * before we get to this point. */ - memset_after(&txinfo->status, 0, rates); + memset(&txinfo->pad, 0, sizeof(txinfo->pad)); + memset(&txinfo->rate_driver_data, 0, sizeof(txinfo->rate_driver_data)); if (atomic_read(&ar->tx_total_queued)) ar->tx_schedule = true;